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lossless_common.h (8435B)

      1 // Copyright 2012 Google Inc. All Rights Reserved.
      2 //
      3 // Use of this source code is governed by a BSD-style license
      4 // that can be found in the COPYING file in the root of the source
      5 // tree. An additional intellectual property rights grant can be found
      6 // in the file PATENTS. All contributing project authors may
      7 // be found in the AUTHORS file in the root of the source tree.
      8 // -----------------------------------------------------------------------------
      9 //
     10 // Image transforms and color space conversion methods for lossless decoder.
     11 //
     12 // Authors: Vikas Arora (vikaas.arora@gmail.com)
     13 //          Jyrki Alakuijala (jyrki@google.com)
     14 //          Vincent Rabaud (vrabaud@google.com)
     15 
     16 #ifndef WEBP_DSP_LOSSLESS_COMMON_H_
     17 #define WEBP_DSP_LOSSLESS_COMMON_H_
     18 
     19 #include <assert.h>
     20 #include <stddef.h>
     21 
     22 #include "src/dsp/cpu.h"
     23 #include "src/utils/utils.h"
     24 #include "src/webp/types.h"
     25 
     26 #ifdef __cplusplus
     27 extern "C" {
     28 #endif
     29 
     30 //------------------------------------------------------------------------------
     31 // Decoding
     32 
     33 // color mapping related functions.
     34 static WEBP_INLINE uint32_t VP8GetARGBIndex(uint32_t idx) {
     35  return (idx >> 8) & 0xff;
     36 }
     37 
     38 static WEBP_INLINE uint8_t VP8GetAlphaIndex(uint8_t idx) {
     39  return idx;
     40 }
     41 
     42 static WEBP_INLINE uint32_t VP8GetARGBValue(uint32_t val) {
     43  return val;
     44 }
     45 
     46 static WEBP_INLINE uint8_t VP8GetAlphaValue(uint32_t val) {
     47  return (val >> 8) & 0xff;
     48 }
     49 
     50 //------------------------------------------------------------------------------
     51 // Misc methods.
     52 
     53 // Computes sampled size of 'size' when sampling using 'sampling bits'.
     54 static WEBP_INLINE uint32_t VP8LSubSampleSize(uint32_t size,
     55                                              uint32_t sampling_bits) {
     56  return (size + (1 << sampling_bits) - 1) >> sampling_bits;
     57 }
     58 
     59 // Converts near lossless quality into max number of bits shaved off.
     60 static WEBP_INLINE int VP8LNearLosslessBits(int near_lossless_quality) {
     61  //    100 -> 0
     62  // 80..99 -> 1
     63  // 60..79 -> 2
     64  // 40..59 -> 3
     65  // 20..39 -> 4
     66  //  0..19 -> 5
     67  return 5 - near_lossless_quality / 20;
     68 }
     69 
     70 // -----------------------------------------------------------------------------
     71 // Faster logarithm for integers. Small values use a look-up table.
     72 
     73 // The threshold till approximate version of log_2 can be used.
     74 // Practically, we can get rid of the call to log() as the two values match to
     75 // very high degree (the ratio of these two is 0.99999x).
     76 // Keeping a high threshold for now.
     77 #define APPROX_LOG_WITH_CORRECTION_MAX  65536
     78 #define APPROX_LOG_MAX                   4096
     79 // VP8LFastLog2 and VP8LFastSLog2 are used on elements from image histograms.
     80 // The histogram values cannot exceed the maximum number of pixels, which
     81 // is (1 << 14) * (1 << 14). Therefore S * log(S) < (1 << 33).
     82 // No more than 32 bits of precision should be chosen.
     83 // To match the original float implementation, 23 bits of precision are used.
     84 #define LOG_2_PRECISION_BITS 23
     85 #define LOG_2_RECIPROCAL 1.44269504088896338700465094007086
     86 // LOG_2_RECIPROCAL * (1 << LOG_2_PRECISION_BITS)
     87 #define LOG_2_RECIPROCAL_FIXED_DOUBLE 12102203.161561485379934310913085937500
     88 #define LOG_2_RECIPROCAL_FIXED ((uint64_t)12102203)
     89 #define LOG_LOOKUP_IDX_MAX 256
     90 extern const uint32_t kLog2Table[LOG_LOOKUP_IDX_MAX];
     91 extern const uint64_t kSLog2Table[LOG_LOOKUP_IDX_MAX];
     92 typedef uint32_t (*VP8LFastLog2SlowFunc)(uint32_t v);
     93 typedef uint64_t (*VP8LFastSLog2SlowFunc)(uint32_t v);
     94 
     95 extern VP8LFastLog2SlowFunc VP8LFastLog2Slow;
     96 extern VP8LFastSLog2SlowFunc VP8LFastSLog2Slow;
     97 
     98 static WEBP_INLINE uint32_t VP8LFastLog2(uint32_t v) {
     99  return (v < LOG_LOOKUP_IDX_MAX) ? kLog2Table[v] : VP8LFastLog2Slow(v);
    100 }
    101 // Fast calculation of v * log2(v) for integer input.
    102 static WEBP_INLINE uint64_t VP8LFastSLog2(uint32_t v) {
    103  return (v < LOG_LOOKUP_IDX_MAX) ? kSLog2Table[v] : VP8LFastSLog2Slow(v);
    104 }
    105 
    106 static WEBP_INLINE uint64_t RightShiftRound(uint64_t v, uint32_t shift) {
    107  return (v + (1ull << shift >> 1)) >> shift;
    108 }
    109 
    110 static WEBP_INLINE int64_t DivRound(int64_t a, int64_t b) {
    111  return ((a < 0) == (b < 0)) ? ((a + b / 2) / b) : ((a - b / 2) / b);
    112 }
    113 
    114 #define WEBP_INT64_MAX ((int64_t)((1ull << 63) - 1))
    115 #define WEBP_UINT64_MAX (~0ull)
    116 
    117 // -----------------------------------------------------------------------------
    118 // PrefixEncode()
    119 
    120 // Splitting of distance and length codes into prefixes and
    121 // extra bits. The prefixes are encoded with an entropy code
    122 // while the extra bits are stored just as normal bits.
    123 static WEBP_INLINE void VP8LPrefixEncodeBitsNoLUT(int distance, int* const code,
    124                                                  int* const extra_bits) {
    125  const int highest_bit = BitsLog2Floor(--distance);
    126  const int second_highest_bit = (distance >> (highest_bit - 1)) & 1;
    127  *extra_bits = highest_bit - 1;
    128  *code = 2 * highest_bit + second_highest_bit;
    129 }
    130 
    131 static WEBP_INLINE void VP8LPrefixEncodeNoLUT(int distance, int* const code,
    132                                              int* const extra_bits,
    133                                              int* const extra_bits_value) {
    134  const int highest_bit = BitsLog2Floor(--distance);
    135  const int second_highest_bit = (distance >> (highest_bit - 1)) & 1;
    136  *extra_bits = highest_bit - 1;
    137  *extra_bits_value = distance & ((1 << *extra_bits) - 1);
    138  *code = 2 * highest_bit + second_highest_bit;
    139 }
    140 
    141 #define PREFIX_LOOKUP_IDX_MAX   512
    142 typedef struct {
    143  int8_t code;
    144  int8_t extra_bits;
    145 } VP8LPrefixCode;
    146 
    147 // These tables are derived using VP8LPrefixEncodeNoLUT.
    148 extern const VP8LPrefixCode kPrefixEncodeCode[PREFIX_LOOKUP_IDX_MAX];
    149 extern const uint8_t kPrefixEncodeExtraBitsValue[PREFIX_LOOKUP_IDX_MAX];
    150 static WEBP_INLINE void VP8LPrefixEncodeBits(int distance, int* const code,
    151                                             int* const extra_bits) {
    152  if (distance < PREFIX_LOOKUP_IDX_MAX) {
    153    const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance];
    154    *code = prefix_code.code;
    155    *extra_bits = prefix_code.extra_bits;
    156  } else {
    157    VP8LPrefixEncodeBitsNoLUT(distance, code, extra_bits);
    158  }
    159 }
    160 
    161 static WEBP_INLINE void VP8LPrefixEncode(int distance, int* const code,
    162                                         int* const extra_bits,
    163                                         int* const extra_bits_value) {
    164  if (distance < PREFIX_LOOKUP_IDX_MAX) {
    165    const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance];
    166    *code = prefix_code.code;
    167    *extra_bits = prefix_code.extra_bits;
    168    *extra_bits_value = kPrefixEncodeExtraBitsValue[distance];
    169  } else {
    170    VP8LPrefixEncodeNoLUT(distance, code, extra_bits, extra_bits_value);
    171  }
    172 }
    173 
    174 // Sum of each component, mod 256.
    175 static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE
    176 uint32_t VP8LAddPixels(uint32_t a, uint32_t b) {
    177  const uint32_t alpha_and_green = (a & 0xff00ff00u) + (b & 0xff00ff00u);
    178  const uint32_t red_and_blue = (a & 0x00ff00ffu) + (b & 0x00ff00ffu);
    179  return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);
    180 }
    181 
    182 // Difference of each component, mod 256.
    183 static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE
    184 uint32_t VP8LSubPixels(uint32_t a, uint32_t b) {
    185  const uint32_t alpha_and_green =
    186      0x00ff00ffu + (a & 0xff00ff00u) - (b & 0xff00ff00u);
    187  const uint32_t red_and_blue =
    188      0xff00ff00u + (a & 0x00ff00ffu) - (b & 0x00ff00ffu);
    189  return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);
    190 }
    191 
    192 //------------------------------------------------------------------------------
    193 // Transform-related functions used in both encoding and decoding.
    194 
    195 // Macros used to create a batch predictor that iteratively uses a
    196 // one-pixel predictor.
    197 
    198 // The predictor is added to the output pixel (which
    199 // is therefore considered as a residual) to get the final prediction.
    200 #define GENERATE_PREDICTOR_ADD(PREDICTOR, PREDICTOR_ADD)                 \
    201 static void PREDICTOR_ADD(const uint32_t* in, const uint32_t* upper,     \
    202                          int num_pixels, uint32_t* WEBP_RESTRICT out) { \
    203  int x;                                                                 \
    204  assert(upper != NULL);                                                 \
    205  for (x = 0; x < num_pixels; ++x) {                                     \
    206    const uint32_t pred = (PREDICTOR)(&out[x - 1], upper + x);           \
    207    out[x] = VP8LAddPixels(in[x], pred);                                 \
    208  }                                                                      \
    209 }
    210 
    211 #ifdef __cplusplus
    212 }    // extern "C"
    213 #endif
    214 
    215 #endif  // WEBP_DSP_LOSSLESS_COMMON_H_